Evidence for FSH-like material in ACTH granules of certain corticotropic cells in the pituitary of the pig.

The ultrastructural immunocytochemical peroxidase-antiperoxidase technique used on serial sections reveals that certain corticotropic cells contain both ACTH and FSH beta, but not LH beta (ACTH/FSH cells). To determine the specificity of the anti-FSH beta staining in these cells, immunocytochemical absorption experiments were performed. The results indicate that (1) anti-FSH beta and -ACTH antisera are bound to different antigens in the corticotropic cell, and (2) anti-FSH beta staining is specific for a FSH-like antigen. In the ACTH/FSH cells both hormones are stored in the same secretory granules, distributed among other granules that contain only ACTH.